1. Field of the Invention
The present invention relates to an apparatus and method for ultrasonic communication. More particularly, the present invention relates to an apparatus and method for ultrasonically communicating data from a source to a destination, ultrasonically acknowledging receipt of the data, and displaying the data at the destination. A particular application of the invention is to ultrasonically communicate price information from a computer to a remote display device, such as an electronic shelf label, ultrasonically acknowledge receipt of the information by the display device, and display the food price information on the display device. A novel application of digital signal processing enables the acknowledgement transmission to not consume much power.
2. Description of Related Art
Technology is becoming more and more prevalent in retail consumer transactions. At checkout stations, for example, automatic detection of price information on bar coded items is now commonplace. A more recent advance is the use of electronic shelf edge labels to display food item and/or price information for shelved items. In this way, pricing information for the shelved items may be electronically updated rather than manually updating printed shelf labels.
Electronic shelf edge labels available today typically require manual entry of data or remote entry via radio, light, or direct-connect communication. U.S. Pat. No. 5,019,811, assigned to Unigrafic AG, for example, discusses the use of a radio connection or an infrared connection between a computer or control device and an electronic shelf label. U.S. Pat. No. 4,002,886, issued to R. M. Sundelin, relates primarily to a direct-connect system for communicating price information from a computer to an electronic price display unit.
Unfortunately, a radio link is expensive and therefore the number of radio transceivers per shelf or gondola is typically limited to one. Individual shelf edge labels are then physically connected by wires or snap-in tracks to the radio transceiver, negating the ability to directly communicate with individual labels. Furthermore, radio links are increasing to the point that channels are beginning to interfere with each other. This interference threatens the reliability of existing and future radio links.
Direct communication with individual labels is illustrated by the light-based ILID system by Technical Computing & Graphics (TCG) Systems Automation Marketing. The ILID system communicates with individual labels by flickering florescent lights in the store. Communication is one-way only, however. Labels do not transmit information.
In general, existing systems suffer from a number of disadvantages sought to be addressed by the present invention. By way of example, some existing systems do not provide for two-way communication. Labels cannot acknowledge receipt of data. Also, light based systems are disadvantageous because of the distraction inherent in flickering lights and because shadows render some labels inactive. Another disadvantage of some current systems is that they require line-of-sight communication between the source and destination (such as antennas or wiring to gondolas).